[experiment] add alternative wasm sqlite3 implementation available via build-tag (#2863)

This allows for building GoToSocial with [SQLite transpiled to WASM](https://github.com/ncruces/go-sqlite3) and accessed through [Wazero](https://wazero.io/).

vendor/github.com/ncruces/go-sqlite3/internal/util/handle.go

@@ -0,0 +1,65 @@
+package util
+
+import (
+	"context"
+	"io"
+)
+
+type handleState struct {
+	handles []any
+	holes   int
+}
+
+func (s *handleState) CloseNotify(ctx context.Context, exitCode uint32) {
+	for _, h := range s.handles {
+		if c, ok := h.(io.Closer); ok {
+			c.Close()
+		}
+	}
+	s.handles = nil
+	s.holes = 0
+}
+
+func GetHandle(ctx context.Context, id uint32) any {
+	if id == 0 {
+		return nil
+	}
+	s := ctx.Value(moduleKey{}).(*moduleState)
+	return s.handles[^id]
+}
+
+func DelHandle(ctx context.Context, id uint32) error {
+	if id == 0 {
+		return nil
+	}
+	s := ctx.Value(moduleKey{}).(*moduleState)
+	a := s.handles[^id]
+	s.handles[^id] = nil
+	s.holes++
+	if c, ok := a.(io.Closer); ok {
+		return c.Close()
+	}
+	return nil
+}
+
+func AddHandle(ctx context.Context, a any) (id uint32) {
+	if a == nil {
+		panic(NilErr)
+	}
+	s := ctx.Value(moduleKey{}).(*moduleState)
+
+	// Find an empty slot.
+	if s.holes > cap(s.handles)-len(s.handles) {
+		for id, h := range s.handles {
+			if h == nil {
+				s.holes--
+				s.handles[id] = a
+				return ^uint32(id)
+			}
+		}
+	}
+
+	// Add a new slot.
+	s.handles = append(s.handles, a)
+	return -uint32(len(s.handles))
+}